Study of the dynamic in granular systems by numerical simulation using particle and finite volume approaches

Abstract

The proposed work aims at developing theoretical and computational simulations involving the dynamics of granular systems. The main focus is the analysis of the contact forces between particles of granular materials using continuum models based on soil mechanics and kinetic theory of granular flow (large systems with many particles, Eulerian formulation - Finite Volume) and discrete models based on physical characteristics of materials (intermediate systems and a limited number of particles, Lagrangian - Discrete Element Method). During my studies, I intend to discuss with Professor R. A. Scott (The University of Michigan) the development of models based on continuous and discrete particle interactions that characterize the dynamics of granular systems with vibrations. I expect to contribute to the improvement of the literature existing models (for the continuous case - model of Srivastava and Sundaresan, 2003, and for the discrete case - model Johnson, 1985, see details in the full research project). In the future, these new formulations will also be tested in fluidized gas-solid flows. I currently have a project in fluidized bed approved by FAPESP. Among the many applications of granular systems, it can be listed: the natural processes of erosion, sedimentation, dune formation, and industrial processes in the pharmaceutical and chemical industries. In these industries, the mechanisms of flow can promote mixing of powders in the manufacture of medicinal products. The process of vibration increases the flow rate and the flow of the solid discharge of silos. Although the chemical reactions and heat transfer mechanisms influencing these applications, granular systems are dominated by hydrodynamic processes, which determine the spatial and temporal distribution of phases and species involved. As the hydrodynamic is dominant in the transport processes of mass and energy in certain temporal and spatial scales, it is essential its study and its understanding for the development of chemical and thermal processes. Due to the complexity of physical phenomena, even at the present understanding of the dynamics and the basic hydrodynamic processes occurring in granular flows in industrial installations is incomplete and insufficient. The purpose of this work is to use the source code MFIX ("Multiphase Flow with Interphase eXchanges") of Syamlal et al. (Syamlal, M. Rogers, W. O'Brien, T. MFIX documentation: theory guide, Technical Note, DOE/METC-95/1013, 1993, www.mfix.org) written in the Fortran programming language. In order to study the contact forces, the main problems to be analyzed will be the discharge systems consisting of particles of different diameters, different geometries of the silos, and other variables. These hopper-type systems may be subject to vibration of the walls to facilitate mixing of the solid. Thus, by using this code I intend to perform computer simulations of the dynamics of granular systems, analyzing the contact forces among particles. The results obtained with the MFIX code will be compared with experimental and numerical data from the literature. I have been supervising several studies in this area such as: a scientific initiation and two Ph.D., one in gas-solid flow and another in granular flows. Upon returning to Brazil, I will continue running the project from FAPESP, and future work will be proposed to the physical formulations derived from the six months at University of Michigan. (AU)